Hydraulic positional control system

ABSTRACT

An hydraulic control system having a master and load cylinder, the latter positioning a control shaft in response to movements of the former. The control system has a separate auxiliary circuit which automatically returns the load piston to its neutral position each time the master piston passes through a predetermined position and an unsynchronized condition between the master and load pistons is sensed. A mechanical linkage, which interconnects hydraulic elements of the two hydraulic circuits, senses the unsynchronized condition; and the auxiliary circuit upon indication of an unsynchronized condition returns the load piston to its neutral position.

Fischer 1 Oct. 1, 1974 1 1 HYDRAULIC POSllTIONAlL CONTROL SYSTEM [76] inventor: Stephen J. Fischer, 5805 Mayhurst Dr., Hyattsville, Md. 20782 [22] Filed: Feb. 20, 1973 [21] Appl. No.: 333,921

[52] US. Cl. 91/368, 60/573 [51] Int. Cl. .Q FlSb 9/10 [58] Field of Search 60/573, 572, 571; 91/374, 91/368 [56] References Cited UNITED STATES PATENTS 2,243,385 5/1941 Levy 60/573 2,368,659 2/1945 Heineck et al..... 60/573 2,410,978 11/1946 Kelly 60/572 2,854,187 9/1958 Crooks 91/374 3,475,911 11/1969 Harrison 60/573 3,579,989 5/1971 Stork et a1. 60/573 FOREIGN PATENTS OR APPLICATIONS 1,185,494 2/1959 France 60/571 24 26 30 1 F g i 26 Primary Examiner1rwin C. Cohen Assistant Examiner-A. M. Zupac v Attorney, Agent, or Firm-R. S. Sciascia; P. Schneider; R. B. Rothman [5 7 ABSTRACT ments of the two hydraulic circuits, sensesft he uns y nchronized condition; and the auxiliary circuit upon indication of an unsynchronized condition returns the load piston to its neutral position.

6 Claims, 2 Drawing Figures a a /4 a t as 44 BACKGROUND OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the hydraulic control The present invention relates generally to hydraulic System includes an l or control Stick 2 c control systems and more particularly to an hydraulic control system for guiding movements of control surfaces on a sea vessel.

Most submarine hydraulic control systems have a normal control system under the control of an electri cally actuated servo control valveand an emergency system under the control of a simple directional control valve. The electrical system has had a record of a number of failures and malfunctions in the past. The emergency control system, while reliable, has often been slow to be placed in operation because of delays in the failure. recognition circuit. Such emergency control-systems are not responsive since they require the operator to displace a stick to move control surfaces and to bring the stick back to neutral to stop them. This requirement is extremely demanding on an operator in a rough sea.

Hydraulic positional control systems have been employed to obviate these failings. However, centering springs play an important role in the presently operational system. The force, which such springs exert, can

vary withtim'e or operating conditions and, therefore, I

introduces error into the system. Also the spring force becomes relatively small as control pistons near their neutral position. This fact makes control near neutral subject to errors and slow response.

SUMMARY OF THE INVENTION between the master and load pistons due to the ever present normal system leakage. Upon sensing such a condition, the auxiliary circuit hydraulically returns the linkage and thus the master and load pistons to their synchronized position.

OBJECTS OF THE INVENTION An object of the present invention is to provide an all-hydraulic positional control system.

Another object is to provide a cyclic check on the relative alignment of a master and load piston and to correct any misalignment due to normal system leakage.

Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of the hydraulic control system of the present invention; and

FIG. 2 is a schematic of the control system in an unsynchronized position.

cally interconnected to a linkage 4. Linkage 4'en ters master cylinder 8 and is connected to master piston 6. Master cylinder 8 is filled with hydraulic fluid, and connected via lines 10 and 12 to follow cylinder 14 having a follow-cylinder piston 16; mounted therein. The follow cylinder piston 16 is connected via linkages 18, 22 and 26 to load control valve 28 having a control spool 30 mounted therein. The load control valve is connected via lines 32 to the right and left sides of load cylinder 34. Hydraulic fluid under high pressure, supplied through line 36 and load control valve 28 to either side of load cylinder 34, moves load cylinder piston 38 from its neutral position shown by the dotted line 40. Movement of load cylinder piston 38 displaces shaft 42 which, in turn, is connected to some control surface (not shown) to be moved.

An auxiliary hydraulic circuit is mechanically interconnected to the-primary hydraulic circuit described above. This auxiliary circuit includes a single position make-up valve 44, hydraulically interconnected via supply line 46 and return line 47 to directional makeup valve 48. The single position make-up valve 44 is mechanically interconnected to control stick 2 via linkages 50 and 88 and stationary support number 52. The directional make-up valve 48 is mechanically interconnected via linkage 54 and stationary support member 56 to the primary hydraulic circuit.

A better understanding of the invention may be gained through a description of its operation. Assume that the control stick and the load piston 38 are initially both in the neutral position as shown inFIG. 1. In this position the system is in alignment. If the handle of the control stick 2 is displaced to the right, master piston 6 will move to the right, and spool 60 in the single position make-up valve 44 will move to the left. Movement of the spool 60 in the left or right directions will cut off the supply of pressurized hydraulic fluid from line 62 to supply line 46 and the return of hydraulic fluid from line 47 to return line 64.

Displacement of the master piston 6 to the right forces hydraulic fluid into the left end of the follow cylinder 14 via line 12. Hydraulic fluid displaced from the right end of follow cylinder 14 flows into the left end of the master cylinder 8. Since the load piston 38 is at rest, linkage 22 will pivot around point 66 moving the load control valve spool 30 to the right. Point 68 will be moved to the left by this action; however, since the lines 46 and 47 are blocked, opening of the directional make-up valve 48 will, at this point, have no effect.

Movement of the load control valve 28 to the right allows pressurized hydraulic fluid from supply line 36 to flow through line 32 to the right side of load cylinder 34, which fluid will move the load cylinder piston 38 to the left. Hydraulic fluid displaced from the left end of the load cylinder 34 will travel through left line 32 and return line 70 to a sump (not shown). Movement of the load cylinder piston 38 to the left moves shaft 42 and linkage 72 which is mechanically and pivotally connected to the load control valve 28. This displacement will move load control valve 28 in the direction opposite to its original displacement and eventually to its center position, as shown, shutting off any flow. At this point movement of the load cylinder piston 38 stops and the load cylinder piston is in its ordered position. if one could count on the input'control stick 2 and the load cylinder piston 38 always being in alignment, the auxiliary hydraulic control system would be unnecessary. However, misalignment is bound to occur due to the ever present normal system leakage. The auxiliary system of the present invention corrects for this misalignment.

To illustrate the problem, assume next that the input control stick 2 is moved back to its center or neutral position, and the load cylinder piston 38 has stopped moving but is to the left of its neutral position 40 due to system leakage as depicted in FIG. 2. Since the load cylinder piston 38 is at rest, the load control valve 28 is centered; but the follow cylinder piston 16 due to linkage 22 .is to the right of its neutral position. This misalignment is sensed through linkage 54 which causes the directional make-upvalve 48 to be to the left of its neutral position. Under these conditions the purpose of the single position make-up valve 44, which is now open since the control stick 2 has been moved back to its neutral position, and the directional makeup valve 48comes into focus. Control stick 2 may be held or otherwise retained in neutral position.

The single position make-upvalve 44 being in its open position, pressurized fluid from a source (not shown) is supplied to line 62, through valve 44.to line 46, and directional make-up valve 48. The directional make-up valve 48 will direct the fluid through line 80 to the right side of follow cylinder 14 moving follow cylinder piston 16 back to its neutral position. The hydraulic fluid displaced from the left side of follow cylinder 14 flows through single position make-up valve 44 to return line 64. Movement of the follow cylinder piston 16 displaces the load control valve to the left through linkage 22. The displacement of the load control valve directs hydraulic fluid to the left side of the load cylinder moving the load piston back to its neutral position 40. Again, movement of linkages 72, 84 and.

26 connecting the load cylinder piston 38 to the load control valve will shut the latter off when the load cylinder piston reaches its neutral position. The control system has thus been realignedfboth the input lever and the load cylinder piston being in the neutral position.

For purposes of illustration the various linkage members shown in the drawings are depicted as being connected simply by pins. Of course, if this were the case, the linkages would bind. For example, as linkage member 2 is rotated, the vertical distance between linkages 4 and 88 would decrease. This problem can be remedied quite simply by using a slot and pin connection at point 3 and a bifurcated end and pin connection at points 89, 68, 20 and 43, as would be apparent to those skilled in theart.

It may be further noted that although in the present illustration the alignment correction occurs onlywhen the control stick -2 moves through its center position, any other neutral position can be chosen simply by adjusting the open position of the single position make-up valve 60 relative to the control stick position. This could be accomplished, for example, by providing a threaded adjustable connection in linkages 88 and 67. Although in the preferred embodiment the load control valve is connected to a 3,000 psi constant pressure source and the single position make-up valve is connected to a psi constant pressure source, the. pressures and type of pressure sources may vary. Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An hydraulic positional control system comprising;

a master cylinder having a master piston mounted therein, said master piston having a neutral position intermediate the ends'of said master cylinder;

a load cylinder having a load piston mounted therein, said master piston and said load piston normally being aligned with one another;

input means for moving said master piston;

a follow cylinder hydraulically interconnected to said master cylinder;

a follow cylinder piston mounted in said follow cylinder, said follow cylinder piston having a neutral position intermediate the ends of said follow cylinder;

a load control valve mechanically connected to said follow cylinder piston for controlling the flow of a pressurized fluid to said load cylinder for moving said load piston from a neutral position;

a shaft connected to said load piston;

means connected to said shaft for progressively closing said load control valve as said shaft moves, to thereby stop movement of the load piston and shaft substantially in fixed proportion to movements of said master piston; and

auxiliary hydraulic means for sensing and causing correction of any misalignment between said master piston and said load piston as said master piston moves through its neutral position.

2. The control system of claim 1 wherein the auxiliary hydraulic means comprises:

a single position make-up valve mechanically connected to said input means;

means for opening said single position make-up valve when said master piston moves through its neutral position;

' a directional make-up valve hydraulically connected to said follow cylinder for directing a flow of pressurized fluid to said follow cylinder to move said follow cylinder piston;

means connected to said follow cylinder piston for opening said directional make-up valve when said follow cylinder piston moves from its neutral position; and

a supply line connected atone end to said single position make-up valve and at the other end to said directional make-up valve.

3. The control system of claim 2 wherein both opening means comprise mechanical linkage means.

4. The control system of claim 1 wherein the auxiliary hydraulic means is connected to said load cylinder piston and said master piston through a plurality of mechanical linkages.

5. The control system of claim 4 wherein the neutral position of said load piston is substantially the center of said load cylinder and the neutral position of said master piston is substantially the centerof said master cylinder.

6. The control system of claim 3 wherein the neutral position of saidload piston is substantially the center of said load cylinder and the neutral position of said master piston is substantially the center of said master cylinder. 

1. An hydraulic positional control system comprising: a master cylinder having a master piston mounted therein, said master piston having a neutral position intermediate the ends of said master cylinder; a load cylinder having a load piston mounted therein, said master piston and said load piston normally being aligned with one another; input means for moving said master piston; a follow cylinder hydraulically interconnected to said master cylinder; a follow cylinder piston mounted in said follow cylinder, sAid follow cylinder piston having a neutral position intermediate the ends of said follow cylinder; a load control valve mechanically connected to said follow cylinder piston for controlling the flow of a pressurized fluid to said load cylinder for moving said load piston from a neutral position; a shaft connected to said load piston; means connected to said shaft for progressively closing said load control valve as said shaft moves, to thereby stop movement of the load piston and shaft substantially in fixed proportion to movements of said master piston; and auxiliary hydraulic means for sensing and causing correction of any misalignment between said master piston and said load piston as said master piston moves through its neutral position.
 2. The control system of claim 1 wherein the auxiliary hydraulic means comprises: a single position make-up valve mechanically connected to said input means; means for opening said single position make-up valve when said master piston moves through its neutral position; a directional make-up valve hydraulically connected to said follow cylinder for directing a flow of pressurized fluid to said follow cylinder to move said follow cylinder piston; means connected to said follow cylinder piston for opening said directional make-up valve when said follow cylinder piston moves from its neutral position; and a supply line connected at one end to said single position make-up valve and at the other end to said directional make-up valve.
 3. The control system of claim 2 wherein both opening means comprise mechanical linkage means.
 4. The control system of claim 1 wherein the auxiliary hydraulic means is connected to said load cylinder piston and said master piston through a plurality of mechanical linkages.
 5. The control system of claim 4 wherein the neutral position of said load piston is substantially the center of said load cylinder and the neutral position of said master piston is substantially the center of said master cylinder.
 6. The control system of claim 3 wherein the neutral position of said load piston is substantially the center of said load cylinder and the neutral position of said master piston is substantially the center of said master cylinder. 